This invention relates to a vibratory finishing machine used for asphalting roads especially suited for maintaining a constant thickness of the layer of asphalt deposited and compacted by the machine itself.
It is known that asphalting work on roads often uses self-propelled machines, called vibratory compactors, which fundamentally consist of a frame, shaped to provide a driver""s cab and housing the machine""s traction means.
The frame also supports a mobile, walled bin containing the hot bitumen aggregate that, retrieved by a conveyor belt, is deposited on the surface being asphalted by the action of a pair of worm screws standing side by side, set crossways to the machine""s direction of travel and made to rotate by a mechanical transmission unit.
While the bitumen aggregate is still hot, it is uniformly distributed over the road coarse and then compacted by means of a device, called a xe2x80x9cvibratory compactorxe2x80x9d, set behind the worm screws with respect to the machine""s direction of travel.
The vibratory compactor is connected to the end of a heavy-duty mechanical arm pivoted on the machine frame and hydraulic jacks on its other end suited to raising and lowering the vibratory compactor according to work needs.
More precisely the vibratory compactor comprises a plowshare element basically consisting of a heavy-duty plate bent to form an L-shape set crossways to the machine""s direction of travel, with the longer wing nearly perpendicular to the road coarse and the shorter wing parallel to the actual coarse.
The plowshare spreads the bitumen aggregate distributed by the worm screws preparing it for compacting by a vertically oscillating beam, which is also set crossways to the machine""s direction of travel and made to vibrate by a device connected to it.
Normally vibratory finishing machines have, next to the two sides of the vibratory compactor device, vertically sliding flat elements that slide and/or scrape along the floor being asphalted and are used to retain the material deposited within the work area of the vibratory compactor.
As is known, the thickness of the asphalt layer depends on the machine""s travel speed and on the thickness of asphalt deposited that is controlled by adjusting the hydraulic jacks that raise/lower a rear heavy-duty arm that supports the plowshare-vibratory elements.
However it may arise for various reasons that the thickness of asphalt layer deposited and compacted undergoes variations during the travel of the vibratory finishing machine, causing unwanted waviness in the runway of the finished road coarse.
To overcome this inconvenience, known technology has fitted the machine with special electronic type, automatic level indicators that, detecting these variations, controls the hydraulic jacks to restore the thickness to the set reference level.
These automatic level indicators are however both complex and costly, and what""s more they are also delicate, considering the harsh work conditions and the consequent risks of wear and tear they undergo during the asphalting process.
The present device will remedy the aforesaid inconveniences.
An object of the present invention is to produce a vibratory finishing machine that will detect the tendency to variation in thickness of the asphalt coarse deposited, with enough time to correct it.
An additional object is to detect the tendency to have various thicknesses and to ensure prompt corrective actions are made with means that have the benefits of being simple, inexpensive and resistant to the risks of wear and tear.
The objectives are achieved by a self-propelled vibratory finishing machine for asphalting road surfaces comprising a frame housing its traction means, being shaped to provide a driver""s cab, and supporting:
storage means for storage and distribution of the bitumen aggregate to be deposited on the aforementioned surfaces;
pressing means for the bitumen aggregate to be deposited, the pressing means is set crossways to the direction of travel of the machine;
flat elements having a primarily longitudinal construction scraping along the surface being asphalted, the flat elements are set on the sides of the machine, they are connected to the pressing means and they are vertically mobile with respect to the pressing means;
such a machine has a means of detection for the thickness of bitumen aggregate deposited, the detection means has first means of reference connected to the flat elements which work together with second means of reference connected to the pressing means. The thickness being measured by the relative deviation between the first and the second means.
According to a preferred form of execution, each means of detection comprises a pointer and a calibrated rule.
According to a variant in execution, the means of detection is connected to an automatic signalling device, being either visual and/or acoustic, of the variation in level.